This invention relates to a mass flowmeter that employs the Coriolis principle and incorporates in at least one section two measuring tubes extending in a common plane, as well as a connecting device by means of which the two measuring tubes are interconnected within the section in which they extend along the said common plane.
Accordingly, the invention relates to Coriolis mass flowmeters that feature at least two measuring tubes which, when not oscillating, extend at least within one section along a common plane, typically parallel to each other. A key aspect in Coriolis mass flowmeters having two or more measuring tubes is the provision of at least one and, where appropriate, two connecting devices as referred to above. These connecting devices determine the effective length of the measuring range since they hold the measuring tubes in position, each defining an oscillation node. Therefore, connecting devices of this type are also known as oscillation node plates.
While the actual measuring zone of the measuring tubes is located between two such oscillation node plates, the intake and, respectively, outlet ends of the measuring tubes in front and in back of the oscillation node plates connect to the pipeline system in which the Coriolis mass flowmeter is installed. These intake and outlet ends of the measuring tubes also contribute to the vibrational isolation of the Coriolis mass flowmeter from the pipeline system.
Apart from defining the effective measuring zone of the Coriolis mass flowmeter, the connecting devices also serve to separate the excitation oscillations of the measuring tubes within the common plane of the measuring tubes from the frequency of perpendicular oscillations. The larger the frequency spacing between these two types of oscillations, the less these oscillations influence each other, which ultimately results in a correspondingly reduced effect on the measuring signal. In that respect, however, Coriolis mass flowmeters with two or more measuring tubes employed in practical application are still in need of improvement since the effect on the excitation oscillations by perpendicular oscillations of the measuring tubes, and thus the interference with the measuring signal, is still too extensive.